1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device including a photosensor. One embodiment of the present invention also relates to a semiconductor device including a photosensor and a display element. In particular, one embodiment of the present invention relates to a semiconductor device including a light-emitting element as a display element. Further, one embodiment of the present invention relates to a driving method of a semiconductor device. Still further, one embodiment of the present invention relates to an electronic device equipped with a semiconductor device.
2. Description of the Related Art
An example of a semiconductor device including a plurality of sensors that detect light (each also referred to as a “photosensor”) arranged in a matrix is a solid-state imaging device (also referred to as an image sensor) used in electronic devices such as digital still cameras or mobile phones.
In particular, a semiconductor device including a plurality of sets each including a photosensor and a display element arranged in a matrix, which has an image displaying function in addition to the imaging function, is also referred to as a touch panel, a touch screen, or the like (hereinafter simply referred to as a “touch panel”). In the touch panel, a region where the sets each including a photosensor and a display element are arranged in a matrix is an image display, data input region.
A touch panel having an image display, data input region where sets each including a photosensor and a display element including an organic light-emitting element are arranged in a matrix has been proposed (see FIGS. 8 and 9 in Patent Document 1).
In the touch panel using such a display element including a light-emitting element, first, the light-emitting elements arranged in a matrix are made to emit light. When an object to be detected exists, the light is blocked by the object and partly reflected. The photosensors arranged in a matrix detect light reflected by the object. In this manner, the touch panel captures an image of the object and detects the position of the object.